Presently used techniques for examination of metals by ultrasonic methods require coupling high frequency (1-5 MHz) energy of a transducer to the material being examined, while maintaining a selected angle of incidence for the ultrasonic beam with respect to the material surface. One method of doing this is by use of an ultrasonic search wheel probe. The search wheel probe consists of a fixed position axle assembly, transducer and thin membrane balloon tire filled with a liquid to couple the sound to the material.
During ultransonic tests using a search wheel, the transducer within the wheel is positioned at a predetermined angle to the material surface, and the wheel is placed in fixed relation on the part being examined, which is wetted to provide coupling. The transducer generates an ultransonic beam and this beam travels from the transducer to the inside of the tire, where both reflection and refraction occur. The refracted beam subsequently enters the part, where defects are detected by monitoring the reflections of this beam. The beam reflected at the inside diameter of the tire may bounce, reflect and refract several times internally in the tire and be interconverted among several sonic modes. The beam entering the material may also encounter similar effects as a result of the material's structure and configuration. Reflections of this beam received during the time interval required for examination of the part may be confused and misinterpreted as defects by the analysis devices.
It is therefore an object of this invention to provide an improved search wheel probe.
Another object of this invention is to provide an improved search wheel probe with limited undesirable reflections of the ultrasonic beam both internal and external to the search wheel.